1. Field of the Invention
This invention relates to a prismatic telescope optical system employing two concentrically mounted telescopes with different magnifications and sharing the same eyepiece and focusing device for a telescope and a viewfinder rotatable inside the telescope.
2. Description of the Prior Art
The prior art is replete with prismatic telescope optical assemblies. For example, U.S. Pat. No. 5,598,296 issued to Imizumi in 1997 disclosed a prismatic telescope optical system including a series of telescopes having different magnification but equal in overall length. The prism optical system of one telescope has a hollow mirror prism and that of another telescope has a glass prism having a proper refractive index.
U.S. Pat. No. 5,548,442 issued to Devenyi et al. in 1996 disclosed an optical sight assembly including a plurality of optical elements moveable into an optical path and a permanent magnet indicating the position of the first or the second set of said optical elements.
U.S. Pat. No. 4,749,271 issued to Nagler in 1998 disclosed a finder scope for use with and spaced apart from the attendant astronomical telescopes.
U.S. Pat. No. 3,572,886 issued to Curtiss et al. in 1971 disclosed a dual power telescope with two portions of a field of view being simultaneously observed and the magnification of each portion differing from that of the other portion.
U.S. Pat. No. 1,530,081 issued to Humbrecht in 1925 disclosed a periscope with entrance and deflection prism with moveable lenses.
U.S. Pat. No. 1,294,365 issued to Bedell in 1919 disclosed a bi-focal periscope with shiftable elements and optical elements operated by power from the compressed air line of the submarine.
U.S. Pat. No. 1,187,818 issued to Cooke in 1916 disclosed a telescope with two powers of magnification and two or more eyepieces or equal length brought to the prism.
U.S. Pat. No. 4,669,883 issued to Mise in 1987 disclosed a spotting scope with a viewer mounted on the telescope.
U.S. Pat. No. 2,619,874 issued to Lane in 1952 disclosed a telescope a viewfinder with prismatic system including four reflecting surfaces and two prisms.
U.S. Pat. No. 841,262 issued to Martin disclosed a binocular prism-telescope with a toothed wheel and a knurled wheel for operating the toothed rims and the tubes.
However, none of the known prior art patents revealed a unique prismatic telescope incorporating a rotating finder scope in its structure as shown in the attached drawings and described herein.